The present disclosure is directed towards a control system for a permanent magnet generator, and more specifically to a passive magnetic flux control for a permanent magnet generator.
Permanent magnet (PM) generators are commonly used to convert rotational movement into electrical power in many areas of vehicle design. If the rotation of a rotor is increased or the power drawn from the connected electronics (the load) is decreased, the generator will increase voltage output, and vice versa. The rotor speed of a PM generator varies with the speed of the mechanical driving component. The speed variation thereby results in variation of the PM generator output voltage.
It is often desirable to have a steady output voltage from a PM generator to provide power to vehicle systems. To maintain a steady output voltage, PM generator assemblies have incorporated active magnetic flux control systems, such as the control system described in U.S. Pat. No. 5,714,823 to Shervington. The Shervington system utilizes a set of control windings alongside the generator windings within the generator that are connected to an active magnetic flux controller. The active magnetic flux controller uses a processor and a detected rotor speed or output voltage and actively determines a control current required to achieve a desirable output voltage. The active controller then outputs the control current to the control windings and thereby controls the resulting output voltage.
When a current travels through the control windings, a magnetic flux is created which permeates the adjacent generator windings. The flux permeation magnetically decouples the generator windings from the rotor. The magnitude of the decoupling depends on the magnitude of current which travels through the control windings, and affects the output voltage of the PM generator. As the magnitude of the decoupling increases, the output voltage of the PM generator decreases. This allows the active controller to input an appropriate current to generate a desired output voltage based on the speed of rotation of the rotor.
While active controllers, such as the one described in Shervington, are generally precise and efficient, they are also expensive to create and calibrate.